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SubjectRe: [PATCH] kernel/signal: Signal-based pre-coredump notification
On Fri, Oct 12, 2018 at 05:33:35PM -0700, Enke Chen wrote:
> For simplicity and consistency, this patch provides an implementation
> for signal-based fault notification prior to the coredump of a child
> process. A new prctl command, PR_SET_PREDUMP_SIG, is defined that can
> be used by an application to express its interest and to specify the
> signal (SIGCHLD or SIGUSR1 or SIGUSR2) for such a notification. A new
> signal code (si_code), CLD_PREDUMP, is also defined for SIGCHLD.
>
> Background:
>
> As the coredump of a process may take time, in certain time-sensitive
> applications it is necessary for a parent process (e.g., a process
> manager) to be notified of a child's imminent death before the coredump
> so that the parent process can act sooner, such as re-spawning an
> application process, or initiating a control-plane fail-over.
>
> Currently there are two ways for a parent process to be notified of a
> child process's state change. One is to use the POSIX signal, and
> another is to use the kernel connector module. The specific events and
> actions are summarized as follows:
>
> Process Event POSIX Signal Connector-based
> ----------------------------------------------------------------------
> ptrace_attach() do_notify_parent_cldstop() proc_ptrace_connector()
> SIGCHLD / CLD_STOPPED
>
> ptrace_detach() do_notify_parent_cldstop() proc_ptrace_connector()
> SIGCHLD / CLD_CONTINUED
>
> pre_coredump/ N/A proc_coredump_connector()
> get_signal()
>
> post_coredump/ do_notify_parent() proc_exit_connector()
> do_exit() SIGCHLD / exit_signal
> ----------------------------------------------------------------------
>
> As shown in the table, the signal-based pre-coredump notification is not
> currently available. In some cases using a connector-based notification
> can be quite complicated (e.g., when a process manager is written in shell
> scripts and thus is subject to certain inherent limitations), and a
> signal-based notification would be simpler and better suited.
>
> Signed-off-by: Enke Chen <enkechen@cisco.com>
> ---
> arch/x86/kernel/signal_compat.c | 2 +-
> include/linux/sched.h | 4 ++
> include/linux/signal.h | 5 +++
> include/uapi/asm-generic/siginfo.h | 3 +-
> include/uapi/linux/prctl.h | 4 ++
> kernel/fork.c | 1 +
> kernel/signal.c | 51 +++++++++++++++++++++++++
> kernel/sys.c | 77 ++++++++++++++++++++++++++++++++++++++
> 8 files changed, 145 insertions(+), 2 deletions(-)

Shouldn't there also be a manpage update, and a kselftest added for this
new user/kernel api that is being created?

thanks,

greg k-h

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